Preventing discoloration in hydrolyzed ethylene-vinyl acetate copolymers

ABSTRACT

A process for the hydrolysis of a solid interpolymer of an ethylenically unsaturated hydrocarbon and a vinyl ester of a 2-6 carbon atom aliphatic carboxylic acid to products having a low yellowness index involves contacting of the solid interpolymer with a substantially anhydrous hydrolyzing agent and subjecting at least one of said interpolymer and said hydrolyzing agent to radiation.

This is a continuation, of application Ser. No. 516,247, filed Oct. 18,1974 now abandoned, which is a division of application Ser. No. 377,997filed July 10, 1973, now U.S. Pat. No. 3,882,005, issued May 6, 1975.

BACKGROUND OF THE INVENTION

Hydrolysis of interpolymers of ethylene and an organic monocarboxylicacid ester of vinyl alcohol is described in U.S. Pat. No. 2,386,347. Theinterpolymer is dissolved in an alkaline liquid medium in which it ishydrolyzed.

Solid phase hydrolysis of a copolymer of an olefinic hydrocarbon and anester of unsaturated alcohol is disclosed in British Pat. No. 1,095,204and U.S. Pat. No. 3,510,463. In this process, the solid copolymer isheated with a hydrolyzing agent, preferably a lower alkyl alcoholcontaining an alkaline reacting catalyst such as an alkali metalalkoxide until alcoholysis is achieved. The solid copolymer does notdissolve but is transformed into the hydrolyzed or alcoholized product.This process is attractive because of its simplicity, but,unfortunately, has one very undesirable feature. The product obtained,especially at high degrees of hydrolysis, is discolored yellow, orange,or golden brown. This color is not readily removed by washing orextracting with alcohols or other solvents. It is undesirable that thehydrolyzed resin product be discolored because the articles moldedtherefrom will also be discolored to a similar extent.

The hydrolysis process is accomplished by an alcoholysis ortransesterification reaction in which, for example, an ethylene-vinylacetate copolymer is converted to the hydrolyzed product and the acetateester of the alcohol used, e.g. methyl acetate from methyl alcohol. Invirtually all cases, the hydrolyzed product is, in fact, a terpolymercomposed of repeating units of ethylene, vinyl alcohol, and a smallamount of unhydrolyzed vinyl acetate. The problem of yellow to orange tobrown discoloration in the hydrolyzed product becomes a serious when thedegree of hydrolysis is relatively high, for example, when, in the caseof ethylene-vinyl acetate copolymers containing 3.50 weight percentvinyl acetate, the hydrolyzed product contains 0.1-15 weight percentresidual vinyl acetate. Usually the color retention is most severe inhydrolyzed products containing 0.1-5% residual vinyl acetate.

The degree of discoloration produced in the solid phase alcoholysis ofethylene-vinyl ester copolymers also becomes more serious as the amountof catalyst used to effect the reaction is increased, or as the volumeof the alcoholysis medium is decreased. Generally, for a given alcoholicmedium, the lower the vinyl ester content of the copolymer, the greaterwill be the amount of catalyst required to effect the hydrolysis in agiven period of time. Consequently, the lower the vinyl ester content ofthe ethylene-vinyl ester copolymer hydrolyzed, the greater will be theamount of discoloration in the product.

We have now found that exposure of the material hydrolyzed and/or thehydrolyzing agent to irradiation acts to prevent the development ofcolor. However, it is not apparent why the irradiation suppresses thecolor build-up in the hydrolyzed resin product. We have found that thehydrolysis medium always becomes discolored yellow to brown as thealcoholysis proceeds whether or not radiation is employed. Evidently,the irradiation does not operate by destroying all color in the medium.Possibly the objectionable color bodies are destroyed selectively orthey are modified in some way such that they are not readily absorbedonto the hydrolyzed resinous product.

It is the object of this invention to provide a process for theproduction of hydrolyzed olefin-vinyl ester interpolymers which arecolorless, i.e., having a yellowness index of less than 30. This andother objects of the invention will become apparent to those of ordinaryskill in the art from the following detailed description.

SUMMARY OF THE INVENTION

This invention relates to hydrolyzed olefin-vinyl ester interpolymersand more particularly to a process for the production of olefin-vinylester interpolymers which have a yellowness index of less than 30 byemploying irradiation, and to the product thus produced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with this invention, an interpolymer of an ethylenicallyunsaturated hydrocarbon and a vinyl ester of a 2-6 carbon atom aliphaticcarboxylic acid is hydrolyzed by means of a substantially anhydroushydrolyzing agent and the interpolymer and/or the hydrolyzing agent issubjected to irradiation.

The ethylenically unsaturated hydrocarbon is generally an alpha-olefinof 2-10 carbon atoms, preferably 2-4 carbon atoms, such as ethylene,propylene, butene, hexene, 2,2,4-trimethyl-pentene-1, and the like.Typical vinyl esters include vinyl formate, vinyl acetate, vinyltrimethyl acetate, vinyl propionate, vinyl butyrate, vinyltrifluoroacetate, and the like. The interpolymers may also contain minoramounts of up to about 5 weight percent of another monomer which can beanother of the aforementioned vinyl esters or carbon monoxide, methylacrylate, n-butyl acrylate, di-n-butyl maleate, diethyl itaconate, andthe like.

The preferred interpolymer employed in this invention is anethylene-vinyl ester copolymer and most preferably an ethylene-vinylacetate copolymer. The copolymers which can conveniently be hydrolyzedby the process of this invention contain from about 1 to about 25 molepercent of the vinyl ester or from about 3 to about 50 weight percentwhen the vinyl ester is vinyl acetate. Most preferably, the copolymerscontain about 3-38 mole percent vinyl ester, or about 8-40 weightpercent when the vinyl ester is vinyl acetate. The vinyl ester contentof the interpolymer can be determined by saponification. The preferredethylene-vinyl ester copolymers have melt flow rates as determined byASTM 1238-65T which broadly vary from about 0.15 g/10 min, as determinedby Condition E to about 25 g/10 min as determined by Condition A. Themelt flow rate under Condition E will hereinafter be termed "meltindex." The copolymers generally have a melt index in the range of about1 to 25.

The interpolymers subjected to hydrolysis in the present process are insolid form. The size and shape of the discrete solid particles can varywidely, e.g., the copolymers may be pulverulent or granular in form.Especially preferred are the ultra-fine powders described in U.S. Pat.No. 3,422,049 which are spherical particles having dimensions in therange of 0.1 to 100 microns.

The interpolymers can conveniently be hydrolyzed in the pellet form inwhich such resins are commonly commercially supplied. Generally, suchpellets are cubical to ovoid in shape and their largest dimension canrange from about 0.5 to as much as 10 mm, although 2-5 mm pellets arepreferred.

The interpolymers can also be in the form of fibers or strands, thediameters of which can range from 0.01 mm to 10 mm and are preferablyabout 0.1 to 5 mm. Films and sheets of the interpolymers can also behydrolyzed. The thickness of such films and sheets can be as low as 0.1mil and as high as 0.5 inch although a range of 1 mil to 0.25 inch ispreferred.

The alcoholic medium required for the hydrolysis reaction is, generally,any primary or secondary alcohol containing up to about 10 carbon atoms.Lower alkyl (1-4 carbon atom) alcohols, such as methyl alcohol, ethylalcohol, n-propyl alcohol, and isopropyl alcohol, are preferred.

If desired, a second organic solvent can be used in conjunction with thealcoholic medium in order to promote the reaction by causing swelling orsoftening of the interpolymer resin. The swelling agents can be a linearor branched, saturated, acyclic hydrocarbon, or a cyclic, saturatedhydrocarbon, containing up to about 10 carbon atoms such as hexane,heptane, octane, decane, diisobutane, cyclohexane, and the like, or anaromatic hydrocarbon containing up to about 12 carbon atoms such asbenzene, toluene, xylene, cumene, pseudocumene, cymene,diisopropylbenzene, and the like.

In all cases, the alcohols and swelling agents must be substantiallyanhydrous in order that the maximum rates of alcoholysis be achieved. Bysubstantially anhydrous is meant a water content of less than about 1%.Preferably, the water content is less than 0.1%.

Additionally, in order to obtain excellent run to run reproducibility,the water content of the reaction medium should be maintainedsubstantially constant, i.e., not varying by more than about 50% andpreferably not more than about 20% as more fully set forth in ourco-pending application Ser. No. 286,788, filed Sept. 6, 1972. Thus, ifthe first run water content is 0.1%, the water content in subsequentruns should be in the range of 0.05-0.15%, preferably 0.08-1.2%. Thesubstantially constant water content can be maintained by controllingthe amount of water in the alcoholic medium and, if used, the secondorganic solvent at low, uniform levels as they are supplied andoperating under a dry, preferably an inert, gaseous blanket, forexample, the liquid feed streams can be dried before use by passagethrough a suitable solid desiccant such as activated molecular sieves,activated alumina or silica gels. The drying is conducted underanhydrous conditions, i.e., under a protective atmosphere of a dry inertgas such as dry nitrogen, argon or helium having a water content belowabout 1000 ppm, preferably below about 300 ppm.

The weight ratio of the alcoholysis medium to interpolymer can vary fromas little as 0.1:1 to as high as 20:1; ratios of 1:1 to 3:1 arepreferred. The amount of alcohol present, however, must be at leaststoichiometric for the amount of alcoholysis which it is desired toaccomplish. Preferably, the amount of alcohol will range from about 2 toabout 100 times the stoichiometric amount of alcohol required.

When a softening solvent is used in combination with the alcohol, theamount of the adjunct used will depend on the nature of the alcohol, thecomposition and molecular weight of the interpolymer, and the nature ofthe softening solvent. Broadly, the alcoholysis medium can contain about1 to 80 weight percent of the softening solvent, preferably 20-40 weightpercent, based on the total weight of the medium. As one example, if theinterpolymer is an ethylene-vinyl acetate copolymer containing about25-30 weight percent vinyl acetate and having a melt index of 1-25, andthe alcohol used in methanol, the alcoholysis medium can contain up to50 weight percent toluene as the softening solvent.

A catalyst is preferably used in the hydrolysis reaction. The preferredcatalyst is an alkali metal alkoxide such as sodium methoxide, lithiummethoxide, and the like, and in general can be any of the sodium,potassium or lithium alkoxides derived from any of the alcohols used asthe alcoholysis medium. Alkali metal hydroxides such as sodiumhydroxide, potassium hydroxide and lithium hydroxide, can also beemployed as catalysts. The amount of catalyst can vary broadly fromabout 0.1 to about 100 weight percent based on the weight of theinterpolymer and is preferably about 1 to 10 weight percent. Highcatalyst/interpolymer weight ratios are sometimes needed when high ratesof hydrolysis are desired or when relatively low amounts of the vinylester are contained in the resin subjected to hydrolysis.

The hydrolysis reaction temperature can vary from about 0° to 250° C.with temperatures of 30° to 100° C. being preferred. Any pressure fromatmospheric to about 5000 psi can be employed so long as it issufficient to maintain the alcoholysis medium in the liquid phase.Reaction times can range from as short as about 1 second to about 24hours; preferred times are from 1 minute to 10 hours.

The irradiation employed in the present invention is electromagneticradiation of wave lengths in the range of about 3000-8000 angstromunits. The radiation can be provided by mercury lamps or fluorescentlamps commercially available for producing near-ultraviolet or "black"light. The mercury lamps are preferred and generally produce light ofnumerous wave lengths in the range of 3000-7600 angstrom units; theprincipal or strongest wave lengths emitted, however, are at 3654angstrom units in the near-ultraviolet and 4358, 5461 and 5780 angstromunits in the visible range. No filter is used with the mercury lamp andthe alcoholysis medium or reaction product is exposed to all wavelengths emitted by the lamp.

The amount of electrical energy supplied to the mercury lamp to effectthe desired suppression of color can vary from about 0.01 to about 100kilowatt hours/liter of alcoholysis medium and is preferably about 0.5to 10 kilowatt hours per liter.

In the preferred embodiment of the invention, the irradiation is appliedto the liquid alcoholysis medium at a point remote from the hydrolysisreactor. This can be accomplished, for example, by circulating themedium from the alcoholysis reactor by means of a pump, through anirradiation chamber, and then back to the alcoholysis reactor. Theirradiation can also be applied to the medium and interpolymer reactionmixture during the hydrolysis reaction. It is also possible to effectcolor removal by a post-alcoholysis irradiation of the hydrolyzedproduct but such a procedure is not preferred because additional timewill be needed for the irradiation procedure and this is noteconomically desirable.

The amount of irradiation applied is not narrowly critical and it ismost convenient to continuously irradiate during the entire hydrolysisreaction. Minimum exposure time depends on numerous factors includingthe nature of the particular interpolymer hydrolyzed, the nature of thealcoholysis medium and, if used, softening solvent, reaction time,reaction pressure, reaction temperature, and the catalyst employed.Determination of the minimum exposure time can be readily determined bythose skilled in the art.

The yellowness indices of the hydrolyzed resin products of thisinvention are calculated according to ASTM D-1925-63T from CIE-1931System tristimulus values determined in accordance with ASTM MethodD-2244-64T with an Automatic Color-Brightness Tester made by MartinSweets, Inc. of Louisville, Kentucky. The tristimulus values weredetermined on 0.25 inch thick placques of hydrolyzed resin productscompression molded at 150° C. within 1-3 days after completion of thealcoholysis reaction. The colormetric measurements themselves werecompleted in a period of 1-5 days after the completion of thealcoholysis reactions. The hydrolyzed resin products and molded placquestherefrom were protected from light before the tristimulus measurementsby keeping them completely wrapped in aluminum foil.

The following Examples are set forth in order to further illustrate theinvention. Unless otherwise specified, all parts and percentages are byweight and all temperatures are in degrees centigrade throughout thisspecification and claims.

EXAMPLE 1 Control Reaction A

A 1-liter, 3-necked Pyrex glass reaction flask was equipped with amechanically-driven paddle stirrer, reflux condenser, oil heating-bathand nitrogen-inlet. The system was initially flushed with nitrogen, andthen a nitrogen atmosphere was established in the flask at a smallpositive pressure (˜2-3 mm Nujol mineral oil) and maintained throughoutthe operations described hereinafter.

Into the flask was introduced 180 ml of methanol followed by 5.20 g(0.226 g-atom) of freshly cut metallic sodium. After the sodium hadcompletely dissolved, there was rapidly added to the resulting sodiummethoxide solution 125.0 g of pellets of an ethylene/vinyl acetatecopolymer having a melt index of 3.3 g/10 min. and a vinyl acetatecontent of 27.7%. Sieve analysis of the pellets showed that all pelletshad passed a No. 5 sieve (nominal opening 4.00 mm) and all retained by aNo. 10 sieve (nominal opening 2.00 mm) of the U.S. Standard Sieve Seriesdescribed by ASTM E11-61. The pellet suspension was then heated toreflux with stirring and the refluxing and stirring was continued forabout 5 hours to effect the desired alcoholysis reaction. Under theseconditions the pellets do not dissolve or coalesce, but graduallyacquire an objectionable yellow-orange color as they are hydrolyzed.

At the end of the 5 hour alcoholysis period, the suspension was cooledbelow the reflux temperature and the brown liquid layer was decantedfrom the hydrolyzed pellets. It was immediately replaced with about anequal volume of 90% aqueous methanol, which was then refluxed withstirring for 15 minutes. The reflux washing procedure was repeated 4more times, whereupon the pellets (110.1 g) were dried overnight in avacuum oven (water aspirator) at about 65° C. Despite the exhaustivewashing procedure, the dried pellets were still dark yellow, the colorbeing uniformly distributed from pellet to pellet. Yellowness index andother properties of this hydrolyzed resin appear in Table I.

This control reaction (no applied irradiation) was carried out in a sumehood illuminated with a 200 watt, glass-encased incandescent light bulblocated about 3 feet overhead. The fume hood was located in a laboratorywhich was illuminated with General Electric "Cool White" fluorescentlamps (No. F96-T-12). The laboratory had two glass windows on the northside.

EXAMPLE 2 Reaction A

The procedure of Example 1 was repeated exactly but a mercury lamp wasplaced 3 inches from the Pyrex reaction flask at a position about 30°above the horizontal. The radiation was continuously applied throughoutthe 5-hour hydrolysis period and also during the reflux-washing with 90%aqueous methanol. After drying, a total of 109.5 g of pellets ofhydrolyzed resin was obtained. The pellets were almost colorless.Yellowness index and other properties of this product are shown in TableI.

The background illumination in this reaction was essentially identicalto the control experiment described in Example 1. The radiation sourceused was a Blak-Ray lamp, model B-100A, supplied by UltravioletProducts, Incorporated of San Gabriel, California. The filter furnishedwith this lamp to provide "black light" was removed and was not used inany of the irradiation described in this or the succeeding Examples. Thebulb used was a 100-watt General Electric mercury lamp (Par 38 SpotBulb, Code II 100 PS44-4). According to the manufacturer, this bulbemits wave lengths between 3000 and 7600 Angstrom Units. Principal wavelengths emitted are 3654, 4358, 5461 and Angstrom units.

EXAMPLE 3 Control Reaction B

Into the reactor described in Example 1 was introduced, under nitrogen,160 ml of methanol followed by 2.00 g (0.087 g-atom) of freshly cutmetallic sodium. When the sodium had dissolved, the temperature of theresulting solution of sodium methoxide in methanol was adjusted to about30° C., whereupon there was rapidly added 100.0 g of pellets of anethylene/vinyl acetate copolymer containing 39.1% vinyl acetate andhaving a melt index of 5 g/10 min. Sieve analysis showed that allpellets passed a No. 5 sieve and all were retained by a No. 10 sieve.The suspension of pellets was heated to reflux with stirring over aperiod of 30 minutes and was thereafter stirred and refluxed for aperiod of 4 hours. The suspension exhibited yellow color after about 45minutes.

After this period, the brown reaction liquid was decanted and replacedwith 200 ml of 90% aqueous methanol and refluxed with stirring for 15minutes to promote removal of sodium salts and yellow color from thepellets. The wash solution was decanted and the washing procedure wasrepeated 4 additional times. After drying overnight in vacuum at 65° C.,there was obtained as a product, 81.3 of g of uniformly yellow pellets.The properties of this resin appear in Table I.

EXAMPLE 4 Reaction B

The procedure of the control reaction B described in Example 3 wasrepeated except that the radiation was applied throughout both the 4.5hour hydrolysis period and washing period by means of the mercury lampdescribed in Example 2. The product of hydrolysis under irradiation was81.6 g of hazy white pellets. No yellow color could be detectedvisually. Properties of this resin are shown in Table I.

EXAMPLE 5 Control Reaction C

Into the reactor described in Example 1 was introduced, under nitrogen,160 ml of methanol followed by 11.6 g (0.290 mol) of U.S.P. sodiumhydroxide pellets. When the sodium hydroxide had dissolved in themethanol, there was added at once 110.0 g of an ethylene/vinyl acetatecopolymer in the form of a powder. The ethylene/vinyl acetate copolymercontained about 19% vinyl acetate and had a melt index of 20 g/10 min.The copolymer had previously been converted to a fine powder by theprocess of U.S. Pat. No. 3,422,049, whereby a powder was produced whichwas substantially all comprised of spherical particles having an averageparticle size of 10-30 microns.

The hydrolysis reaction was continued for 4 hours at reflux whereupon adark yellow slurry was produced. The hydrolyzed powder was collected byfiltration on a Buchner funnel and washed 5 times with 200 ml portionsof methanol to afford, after drying, 99.8 g of light yellow powder.Properties of this hydrolyzed powder are summarized in Table I.Microscopic examination of the hydrolyzed powder showed no agglomerationor substantial change in particle shape had occurred.

EXAMPLE 6 Reaction C

The procedure of Example 5 was repeated but the hydrolysis step wascarried out in the presence of applied irradiation as described inExample 2. The product obtained was a white powder, 103.3 g, describedin detail in Table I.

EXAMPLE 7 Control Reaction D

A 1-liter, 3-necked Pyrex glass reaction flask having a bottom openingthrough a 9 mm stopcock was fitted with a reflux condenser, mechanicallydriven paddle stirrer and nitrogen inlet, and was heated with a suitableheating mantle. Connection was made from the bottom draw-off of thereaction flask to a Pyrex glass coil (8 feet of 10 mm tubing in 12turns) and thence to a circulating pump and back to the reaction flask.Glass tubing and natural rubber tubing were employed to make theconnections. The circulating pump was of the oscillating type and wassupplied by Cole-Parmer Instrument Co. (Model 7103-1). It deliveredabout 1.3 1/min. of methanol in the described set-up. The glass coil wassuspended inside a mirrored Dewar flask (5 inch diameter, 7 inch depth)in such a way that the mercury lamp described in Example 2 could befitted just over the Dewar flask mouth, and about 4-5 inches above theglass coil. In this way it was possible to pump the hot methanolicsodium methoxide solution from the reaction flask through the coilsuspended in the Dewar flask where irradiation took place and then backto the reaction flask. The mercury lamp and Dewar flask irradiationchamber were covered by aluminum foil so that no applied radiation couldreach the resin pellets being hydrolyzed in the reaction flask.Radiation, however, could be applied to the circulating hotmethanolic-sodium methoxide alcoholysis medium in the glass coil so thatdestruction of color-producing bodies could be accomplished therein, ata point remote from the pellets being hydrolyzed in the reaction flask.

400 ml of methanol was introduced into the reaction flask of the abovedescribed apparatus under nitrogen, followed by 5.00 g (0.217 g-atom) offreshly cut metallic sodium. When the sodium had completely dissolved,there was added to the resulting methanolic sodium methoxide solution100 g of pellets of an ethylene/vinyl acetate copolymer of melt index 5g/10 min, and containing 39.1% vinyl acetate. The suspension of pelletswas refluxed with stirring in the reaction flask for a period of 5 hourswhile the methanolic sodium methoxide alcoholysis medium was circulatedsteadily through the glass coil by means of the circulating pump. Noirradiation was applied to the glass coil. The pellets of hydrolyzedcopolymer was recovered by decanting the brown liquid reaction medium,washing 3 times in refluxing 90% aqueous methanol for 15 minutes, anddrying. The recovered hydrolyzed pellets were light yellow and amountedto 81.8 g. They are described more fully in Table II.

EXAMPLE 8 Reaction D

The procedure of Example 7 was repeated, but irradiation from themercury lamp was applied to the methanolic sodium methoxide alcoholysismedium as it passed through the glass coil in the manner indicated inExample 7. The irradiation was continued throughout the 5-hourhydrolysis period and the subsequent washing period as well. Thehydrolyzed pellets amounted to 81.5 g and were nearly colorless. Theirproperties are described in Table II.

EXAMPLE 9 Reaction D¹

The procedure of Example 8 was repeated and except that 125 g of anethylene/vinyl acetate copolymer of melt index 3.2 and containing 27.7%vinyl acetate was alcoholyzed in 400 ml of methanol in which 11.5 g(0.50 g-atom) of metallic sodium had been dissolved. The hydrolyzedresin pellets were washed by stirring for 5 minutes each with threesuccessive fresh portions (200 ml) of continuously circulating methanol.Radiation was applied to the glass coil, as described in Example 8,throughout the reaction and washing operations. After drying there wasobtained 109 g of nearly colorless pellets, described further in TableII.

EXAMPLE 10 Reaction E

This Example illustrates the use of radiation having wave lengths of3000-8000Anstron units to remove color from already hydrolyzed resin.

A 100 g sample of an ethylene/vinyl acetate copolymer (20% vinylacetate) in fine powder form (prepared by method of U.S. Pat. No.3,422,049) was subjected to alcoholysis for 5 hours at reflux in 220 mlof dry methanol in which 4.6 g of metallic sodium had previously beendissolved. The dry, hydrolyzed, pulverulent resin was spread our in a1/16 inch layer and irradiated for 2 hours with unfiltered radiationfrom the mercury lamp described in Example 2, whereupon the powderbecame substantially white or colorless.

EXAMPLE 11 Reaction F

This Example illustrates the use of radiation having wave lengths of3000-8000 Angstrom units to remove color from already hydrolyzed resin.

An ethylene/vinyl acetate copolymer which contained about 43.5% vinylacetate and comprising ovoid pellets having a largest dimension of about1/8 to 7/32 inch was hydrolyzed in methanolic sodium methoxide solution.After prolonged washing with methanol containing methyl acetate producedby the alcoholysis, the pellet product was dried and found to containabout 0.75% residual vinyl acetate and to have a melt index of 7.Despite the washing the pellets had received, they were brown in color.Accordingly, 18.3 g of the brown pellets were spread in single-pelletlayer on the frit of a jacketed Buchner funnel. The mercury lampdescribed in Example 2 was placed over the mouth of the funnel (distance4 inches). With water passing through the jacket of the Buchner funneland an air stream passing upward through the funnel frit, irradiationwas applied for 4 hours. The pellets remained cold during this treatmentand those at the center of the beam became colorless; pellets at theperiphery retained some yellow color.

                                      TABLE I                                     __________________________________________________________________________    ALCOHOLYSIS OF SOLID ETHYLENE/VINYL ACETATE COPOLYMERS                        IRRADIATION FROM MERCURY LAMP APPLIED DIRECTLY TO                             REACTING MIXTURE                                                              __________________________________________________________________________           Ethylene/Vinyl Acetate                                                        Copolymer                Hydrolyzed Product                                                       Mercury                                                   Vinyl               Lamp                Residual                                                                           Melt                             Acetate                                                                            Melt       Wgt.                                                                              Irradi-                                                                            Weight    Yellow-                                                                            Vinyl/                                                                             Index,                           Content,                                                                           Index,                                                                              Physical                                                                           Used,                                                                             ation                                                                              Recovered,                                                                              ness Acetate                                                                            g/10                      Reaction                                                                             %    g/10min                                                                             Form g.  Used g.    Color                                                                             Index                                                                              %    min.                      __________________________________________________________________________    Control A                                                                            27.7 3.3   pellets                                                                            125 no   110.1 dark                                                                              93.9 1.5  2.0                                                             yellow                                  A      27.7 3.3   pellets                                                                            125 yes  109.5 color-                                                                            17.1 1.5  1.2                                                             less                                    Control B                                                                            39.1 5     pellets                                                                            125 no   81.3  yellow                                                                            46.41                                                                              1.5  2.7                       B      39.1 5     pellets                                                                            125 yes  81.6  color-                                                                            25.85                                                                              1.5  2.5                                                             less                                    Control C                                                                            19   20    powder                                                                             110 no   99.8  yellow                                                                            115.67                                                                             0.6  15.0                      C      19   20    powder                                                                             110 yes  103.3 white                                                                             14.95                                                                              1.0  13.4                      __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________    ALCOHOLYSIS OF SOLID ETHYLENE/VINYL ACETATE COPOLYMERS                        IRRADIATION FROM MERCURY LAMP APPLIED TO CIRCULATION                          LIQUID ALCOHOLYSIS MEDIUM AT A POINT REMOTE FROM REACTION                     __________________________________________________________________________           Ethylene/Vinyl Acetate                                                        Copolymer                Hydrolyzed Product                                                       Mercury                                                   Vinyl               Lamp                Residual                                                                           Melt                             Acetate                                                                            Melt       Wgt.                                                                              Irradi-                                                                            Weight    Yellow-                                                                            Vinyl/                                                                             Index,                           Content,                                                                           Index,                                                                              Physical                                                                           Used,                                                                             ation                                                                              Recovered,                                                                              ness Acetate                                                                            g/10                      Reaction                                                                             %    g/10min                                                                             Form g.  Used g.    Color                                                                             Index                                                                              %    min.                      __________________________________________________________________________    Control D                                                                            39.1 5     pellets                                                                            125 no   81.8  light                                                                             34.96                                                                              0.83 2.6                                                             yellow                                  D      39.1 5     pellets                                                                            125 yes  81.5  very                                                                              18.1 0.85 2.4                                                             pale                                                                          yellow                                  D.sup.1                                                                              27.7 3.3   pellets                                                                            125 yes  109   very                                                                              20.9 1.13 3.4                                                             pale                                                                          Yellow                                  __________________________________________________________________________

Various changes and modifications can be made in the process andproducts of the present invention without departing from the spirit andthe scope thereof. The various embodiments described herein werepresented to further illustrate the invention but were not intended tolimit it.

We claim:
 1. A hydrolyzed ethylene-vinyl acetate copolymer having aresidual vinyl acetate content of 0.1 to 15 weight percent, saidhydrolyzed ethylene-vinyl acetate copolymer having a yellowness index(ASTM D-1925-63T) of a specimen thickness of 0.25 inch and having beenprepared byalcoholyzing an ethylene-vinyl acetate copolymer containing8-40 weight percent vinyl acetate and having a melt index in the rangeof from 1 to 25 in suspension in a substantially anhydrous alcoholyzingmedium containing a lower alkanol having from 1 to 4 carbon atoms and analkali metal alkoxide or hydroxide catalyst, and subjecting thealcoholyzing reaction medium containing the copolymer to electromagneticradiation of wave lengths in the range of about 3,000 to 8,000 Angstromunits during at least a portion of the alcoholysis reaction.
 2. Thehydrolyzed ethylene-vinyl acetate copolymer of claim 1, having aresidual vinyl acetate content of 0.1 to 5 weight percent.